Prepare Yumbini with 3/4 cup water according to package directions.
While Yumbini is cooking and cooling, cut the tops off two bell peppers. Remove the core and seeds.
Place bell peppers in a pot with a steamer basket and about 1 inch of water in the bottom. Cover and heat on high until water is boiling. Steam bell peppers 3-5 minutes until slightly soft but not soggy.
Remove the stem and chop the remaining bell pepper tops.
Slice the mushrooms.
Heat the olive oil in a cast iron or stainless frying pan and sauté the mushrooms and chopped bell peppers until lightly browned.
Remove from heat and add the Yumbini and shredded cheese. Mix lightly. It will be a bit sticky but that is what makes it yummy!
Spoon the Yumbini filling into the steamed bell peppers, mounding it up on top.
Bake at 350 for about 20 minutes until piping hot, and the cheese has melted.